Drop-on-demand ink-jet and bubble-jet printers (collectively referred to as ink jet printers) propel from nozzles fine ink droplets onto a paper substrate adjacent the nozzle. An example of these types of printers is the Cannon nozzles known as BC01 and BC02. By precisely controlling the trajectory and the time of ejection of the ink droplets, the ink jet nozzles print clear dots on paper. To achieve such precise positioning of droplets of ink, ink jet nozzles must provide clear and clean orifices for the droplets to pass through as they fly from the nozzle to the surface of the paper. In a conventional drop-on-demand ink jet nozzle, there is an array of several orifices on the face of the nozzle from which the ink droplets are propelled. During printing, ink is ejected out of selected orifices in the array to form the desired images on the paper. The flight of the ink droplets and especially their impact on the paper surface creates a fine mist of ink that coats the surface of the nozzle. Also, during the ejection of the droplets themselves, extraneous ink is sprayed and deposited adjacent the orifices. This moist ink coating attracts paper fiber, dust, grit and other types of particles that can obstruct the nozzle orifices and block the ink droplets being sprayed from the nozzle. Also, the extraneous ink can build up to such an extent that it blocks the orifices. Accordingly, there is a need to regularly clean the nozzle plate of ink jet printers so that the array of orifices remains clear of ink and particles that would otherwise interfere with the printing of ink on the paper.
In the past, ink jet printers have been cleaned by wiper mechanisms that clean the nozzle plates and orifices. Between print jobs, the printer head moves away from the paper web to a cleaning station where is slides against a wiper. These wipers squeegee across the face of the nozzle plate and the openings of the orifices to remove particles that may be obstructing ink in the nozzles. Because the wipers themselves temporarily obstruct the nozzles, the wipers are used only when the ink jet printer is not printing. For example, a wiper may be positioned at the far edges of a carriage path, beyond the edges of the paper held adjacent the carriage path. An example of a wiping system is disclosed in U.S. Pat. No. 5,126,765, entitled "Ink Jet Recording Apparatus Having Cleaning Means For Cleaning A Recording Head". Wipers have proven generally acceptable for desk top printing applications where each individual print job is relatively short and the times between when the print nozzles are wiped clean are relatively brief. In a typical desk-top ink-jet printer the carriage with the ink jet printing head can be shifted to a cleaning station after each print operation. Thus, in the usual desk top application, the printing nozzles are cleaned frequently by conventional wipers and tend not to clog with particles.
With continuous web-feed printing, the print nozzle is required to constantly print for many hours. This is unlike typical desk-top printing applications in which each printing operation is conducted in a relatively short period of time. Shifting the print head to a cleaning station away from the paper to be printed necessarily interrupts the printing operation of a continuous printer. While these interruptions do not substantially interfere with typical desk top print jobs, they do interfere with commercial printing of continuous webs. In this regard, conventional ink jet print heads have been found to require cleaning for every 30 to 60 minutes of printing. Accordingly, remote cleaning stations for ink jet printers are undesirable for commercial continuous printers because the print operation must be interrupted every one-half hour to one hour to clean the nozzles. Accordingly, there is a long-felt need for an apparatus and method for cleaning an ink jet nozzle without interrupting a print job.
Other prior art techniques for cleaning the nozzle face of an ink printer are to blow air at or around the ink nozzles to blow particles off the nozzle face or prevent particles from adhering to the nozzle face. Some of these techniques have included using ionized air to neutralize the static charges on dust particles that attract the dust to the nozzles. These techniques have achieved only partial success as is reported in U.S. Pat. No. 4,411,706, entitled "Method And Apparatus For Eliminating Dust From Ink Jet Printers." While blowing air at the nozzles can be accomplished while the nozzles are spraying ink, (and thus is more advantageous than wipers), the turbulent air flow caused by the blowers disrupts the trajectory of the ink droplets to the paper. Given that the prior systems for cleaning ink jet nozzles have been less than satisfactory, there has been a long felt-need for a technique for effectively cleaning the nozzles. That need was not fully satisfied until the current invention.
The current invention relates to a technique for cleaning an ink jet nozzle with an adsorbent material, such as a thread, that attracts the dust and paper particles that adhere to the face of the nozzle. Particles attach themselves to the thread and cling to the fibers in a thread. Once caught by the thread, the particles can be removed from the area of the nozzles. A thread is movingly positioned across the face of the nozzle of an ink jet printer. The thread is located proximate to the nozzle array from which the ink droplets are propelled. Dust and paper particles that would otherwise clog the nozzle array are caught on the thread before they obstruct the orifices of the nozzle. A dispenser and rewind bobbin arrangement slides the thread in a line(s) across the face of the nozzle to remove the portions of the thread coated with particles and supply clean thread to the nozzle array. By continuously sliding the thread across the nozzle face, ink, grit and paper particles can be continuously captured and removed from the nozzle array. In addition, the ink printer can print while the thread is moving because the thread does not obstruct the ink droplet path from the nozzles to the paper. Accordingly, the current invention provides a technique and apparatus for continually removing particles from an ink jet printer face while printing continues.
In one embodiment, the invention is an ink jet printer head comprising a nozzle plate having an array of orifices through which ink droplets are ejected in a controlled fashion and an ink adsorbent element positioned on said plate in proximity to the array of orifices. In a second embodiment, the invention is a method for cleaning an ink jet printing head having a nozzle plate, an array of orifices in the plate and an ink adsorbent material mounted on the plate proximate to the orifices, wherein the method includes the steps of (a) propelling ink from the orifices of the nozzle plate towards a web for printing on the web; (b) coating the nozzle plate with ink mist and particles while the ink is being propelled from the orifices, and (c) adsorbing at least some of the ink and particles coating the nozzle plate with the adsorbent materials while the ink is being propelled from the orifices.
An object of the current invention is to clean the nozzle array of an ink jet printer and prevent ink, dirt and paper particles from obstructing the orifices of the nozzle array. In this regard, it is a further object of the invention to continually capture and remove ink and particles from the nozzle array while the nozzles are printing. A further object of the invention is to extend the period of maintenance free printing for ink jet printers and to reduce the amount of off-printing cleaning required for ink jet printers. Moreover, another objective of the invention is to enhance the print quality of ink jet printers by overcoming many of the problems caused by extraneous, girt and paper particles that have clogged prior ink jet printers. These and other objectives are achieved by the invention that is shown and described in detail below.